1. Field of the Invention
The present invention relates to a micro light valve for a flat display device, and more particularly to a micro light valve which is corresponding to each of pixel for display and can be controlled by use of electrostatic force to pass or shut a light beam, thereby displaying stationary and moving images, and a method for manufacturing the same.
2. Description of the Prior Art
In various types of light valves for passing or shutting a light beam, there is a liquid crystal display (referred to as "LCD", hereinafter) device using a liquid crystal, as typical light valve. Since such an LCD device is low in power consumption required for passing or shutting of a light beam through liquid crystal therein and is capable of driving a plurality of image pixels independently, the LCD device has been widely used in the display field.
The LCD device, as is widely used as a flat display device, can be operated by low voltage and fabricated with thin film, as compared with a conventional CRT (cathode ray tube) display. Particularly, a thin film transistor LCD device is one of the widely-used micro light valves, because it is capable of embodying a high image quality with respect to various colors.
However, in the case that such an LCD device is fabricated by the up-to-date techniques, several problems occur are as follows:
1. It is difficult to design pixel arrangement for display or to manufacture pixels in proportion to increase of the pixels.
2. As is the case with TFT (Thin Film Transistor) liquid crystal display device having a large panel, it is difficult to manufacture such a display device having a large panel. As a result, the larger the display panel is, the lower yield of the display device is.
3. Since the conventional display device, such as an LCD device, uses liquid crystal material as an intermediation for shutting and passing a light beam, it is difficult to utilize several complicated-processes, such as injection of liquid crystal materials, adjustment of space between two opposite substrates having a liquid crystal layer therebetween, orientation film forming process for arrangement of liquid crystal, or the like. Also, for this reason, cost of the display is very expensive.
4. View angle of the LCD is lower than that of CRT. PA1 5. Since a polarization plate has to be provided in such an LCD, large amount of light is lost.
On the other hand, in the case of mechanical light valves as are developed recently, there is more power consumption, and it is difficult to manufacture such a micro light valve or to make its operation fast. However, with the progress of semiconductor fabrication techniques, micro actuators capable of operating mechanically can be manufactured. Accordingly, if size of such a mechanical light valve can be manufactured extremely small by the semiconductor fabrication techniques, the mechanical light valve permits to pass and to shut off a light beam fast by using little energy.
One pixel of the LCD device is approximately 100 .mu.m.times.100 .mu.m in size, but in the case that each pixel has less than the size, the further small pixel may be sensitively operated by electrostatic force caused by low voltage, as compared to gravity acting upon a body in motion. Therefore, if problems due to a frictional force between two faced bodied in motion can be overcame therein, each pixel having size of less than 100 .mu.m.times.100 .mu.m can be sensitively operated by high electrostatic force fast. This operation has been experimented several times in an electrostatic motor having micron meters of several tens in size.
In paper entitled as "Electrostatic Actuator with Resistive Slider", which is proposed by T. Higuchi and S. Egawa, of 1989 National Convention Record I.E.E., published in Japan, pp 191-192, an electrostatic linear actuator with a movable slider as a resistive body has been applied to move a sheet. This electrostatic actuator has advantages that an electrode is not necessary for a movable slider, and a repelling force as well as a driving force is produced between the slider and a layer, so that a frictional force can be largely reduced. However, such a electrostatic actuator can be manufactured by semiconductor fabrication techniques as well-known in the art. Also, since in the actuator pitch between electrodes is more large and thickness of insulating layer therebetween is very thick, a driving signal of several hundred voltages is necessary for driving of the actuator and it is impossible of driving the actuator fast.